Russia's Maria Sharapova makes a backhand return to Germany's Angelique Kerber during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)

Germany's Angelique Kerber hits a backhand return to Russia's Maria Sharapova during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)

Germany's Alexander Zverev breaks his racket in frustration during his third round match against South Korea's Chung Hyeon at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)

South Korea's Chung Hyeon celebrates after defeating Germany's Alexander Zverev in their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)

United States' Tennys Sandgren celebrates after defeating Germany's Maximilian Marterer during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Ng Han Guan)

United States' Lauren Davis falls during ther third round match against Romania's Simona Halep at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Vincent Thian)

Romania's Simona Halep celebrates after defeating United States' Lauren Davis in their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Ng Han Guan)

United States' Madison Keys makes a backhand return to Romania's Ana Bogdan during their third round match at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 20, 2018. (AP Photo/Dita Alangkara)

MELBOURNE, Australia (AP) — Angelique Kerber is on her own in an elite club at the Australian Open.

The 2016 champion routed Maria Sharapova 6-1, 6-3 in a third-round win that showcased her credentials as a title contender and ensured she'll be the only Grand Slam champion still playing in the second week in the women's draw.

Roger Federer and Novak Djokovic were almost as ruthless in their straight-sets wins Saturday night, which is hardly surprising for two players with a combined 31 Grand Slam titles. As well, it was Federer's 90th match win at Melbourne Park.

Women's No. 1 Simona Halep took a longer route — equaling a mark in Melbourne for endurance but signaling, perhaps, that she's closer to a Grand Slam breakthrough.

Sharapova was back at the Australian Open for the first time since 2016, when a failed doping test led to a 15-month ban from tennis.

After two comfortable wins the five-time major winner was growing in confidence, but she had no answers for Kerber, who is on a 12-match winning streak in a kind of comeback of her own after a sliding down the rankings last year.

"Of course is quite a big match. I mean, Maria is a champion. She's always dangerous, especially at the Grand Slams," Kerber said. "I was really trying to not think about everything around, about against who I'm playing.

"I learned a lot from the last 12, 24 months. I had a great 2016 and last year was a little tougher."

Kerber's year-end ranking dropped from No. 1 in 2016 to 21 last year, when she failed to defend her Australian or U.S. Open titles. "Anybody who knows me knows I never give up."

Sharapova said Kerber was the more aggressive on court and took more risks.

"A lot of things I need to get better at and improve on," she said. "Today was not enough (but) ... looking at the overall picture, there's a lot to build from."

The Kerber-Sharapova match, billed as the showdown of the round, was over quickly. That was in contract to Halep's 4-6, 6-4, 15-13 win in 3 hours and 45 minutes over American Lauren Davis.

The third set took 2 hours, 22 minutes. Halep wasted chances to serve for the match in the ninth, 11th and 15th games, then had to save three match points in the 22nd. There were 11 service breaks and two medical timeouts — for Davis to get treatment on both feet — before Halep converted on her first match point.

"I never played the third set so long, so I'm really happy I could stay and win it. I'm almost dead," Halep said of the match which equaled Chanda Rubin's win over Arantxa Shanchez Vicario in 1996 — also 48 games — for the Australian Open record in terms of most games.

"I just feel that my muscles are gone," said Halep, who badly twisted her left ankle in the first round. "My ankle is, I don't know how it is because I don't feel it anymore!"

Halep will next play Naomi Osaka, who beat 18th-seeded Ash Barty 6-4, 6-2. No. 20 Barbora Strycova beat U.S. qualifier Bernarda Pera 6-2, 6-2, leaving U.S. Open finalist Madison Keys as the only American woman to reach the fourth round.

Kerber's next match is against Hsieh Su-wei, who followed up her win over Wimbledon champion Garbine Muguruza with a 6-2, 7-5 win against No. 26 Agnieszka Radwanska to return to the fourth round at Melbourne Park for the first time in a decade.

Six-time Australian Open champion Djokovic continued his comeback from six months out with an injured right elbow, beating No. 21 Albert Ramos-Vinolas 6-2, 6-3, 6-3.

"I obviously have to be more humble this time with my expectations because I haven't played for six months," said the 14th-seeded Djokovic, who played down the medical time out he took to receive a massage on his back and upper legs as just the tribulations of returning to the tour.

Federer entered the Australian Open last year under similar circumstances, coming off an extended break for a knee injury, and went on to win the title. His defense moved through another round with a 6-2, 7-5, 6-4 win over No. 29 Richard Gasquet.

"Expectations are different," this year, Federer said. "I'm coming in very fit, very well equipped knowing five sets is not an issue. Don't know if (winning) is going to happen this year, but so far, so good."

Tomas Berdych beat 2009 U.S. Open champion Juan Martin del Potro in straight sets and fifth-seeded Dominic Thiem beat Adrian Mannarino to set up a match against Tennys Sandgren.

Djokovic will next face Hyeon Chung, who took out a Zverev for the second time this week. Chung beat fourth-seeded Alexander Zverev 5-7, 7-6 (3), 2-6, 6-3, 6-0 six days after a win over No. 32 Mischa Zverev.

Another loss at a major had the highly-touted Zverev admitting he may have a problem. He's won five tour-level titles, but never gone beyond the fourth round at a major.

"I have some figuring out to do, what happens to me in deciding moments in Grand Slam," he said.